hi i am getting an error while updating data in gridview
Object reference not set to an instance of an object.
i am using this code
Protected Sub gvDetails_RowUpdating(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewUpdateEventArgs) Handles gvDetails.RowUpdating
Dim userid As Integer = Convert.ToInt32(gvDetails.DataKeys(e.RowIndex).Value.ToString())
Dim username As String = gvDetails.DataKeys(e.RowIndex).Values("UserName").ToString()
Dim txtcity As TextBox = DirectCast(gvDetails.Rows(e.RowIndex).FindControl("txtcity"), TextBox)
Dim txtDesignation As TextBox = DirectCast(gvDetails.Rows(e.RowIndex).FindControl("txtstate"), TextBox)
con.Open()
Dim cmd As New OleDbCommand(("update Employee_Details set City='" + txtcity.Text & "',Designation='") + txtDesignation.Text & "' where UserId=" & userid, con)
cmd.ExecuteNonQuery() ...
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